CRISPR-cas system: biological function in microbes and its use to treat antimicrobial resistant pathogens

Abstract

The development of antibiotic resistance in bacteria is a major public health threat. Infection rates of resistant pathogens continue to rise against nearly all antimicrobials, which has led to development of different strategies to combat the antimicrobial resistance. In this review, we discuss how the newly popular CRISPR-cas system has been applied to combat antibiotic resistance in both extracellular and intracellular pathogens. We also review a recently developed method in which nano-size CRISPR complex was used without any phage to target the mecA gene. However, there is still challenge to practice these methods in field against emerging antimicrobial resistant pathogens.

Keywords: Antibacterials; Antimicrobial resistance; CRISPR-cas system; Cas9; Intracellular infection.

Fig. 1

Mechanism of CRISPR-cas immunity divided into three stages. Stage 1: Spacer acquisition. In the first stage specific fragments of virus or plasmid double stranded are integrated at the leader end of CRISPR array on host DNA. A CRISPR array consists of unique spacer (red box) interspaced between repeats (blue box). Spacer acquisition occurs in the presence of cas1 and cas2 proteins, which are present near the vicinity of CRISPR array. Stage 2: Biogenesis of crRNA. In this stage RNA polymerase at leader end helps in the transcription of Pre-CRISPR RNA (Pre-crRNA) to mature crRNA. Stage 3: Interference. In the final stage, specific match between crRNA spacer and target sequence leads to the cleavage of foreign genetic elements (blue and red strips) [14, 15]

Fig. 2

a, b CRISPR-cas9 antibacterials delivery to infected cell. a CRISPR-cas9 antibacterials encoded in bacteriophages. b CRISPR-cas9 encoded in phages were then introduced into the infected host cells to combat AMR pathogens